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2002-2005 Range Rover MkIII / L322
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Discussion Starter #1 (Edited)
TLDR:

TRANS. FAIL SAFE PROG error on dash? Upon diagnostic scan do you get an “Actuator Signal” / “Ground” error code pop up on your transfer case module? Chances are your potentiometer has gone haywire and you need a new TC motor. Potentiometers are not sold separately (up to now, no one has found an alternative to my knowledge), whole TC Actuator motor must be purchased. I bought mine used and luckily the potentiometer in it works and I swapped it into my original TC Actuator motor. It is dead easy to remove the TC Actuator motor and the potentiometer within it.


Hello,

Yesterday while highway driving down a a hill the TRANS. FAIL SAFE PROG. warning came on the dash. I pulled over, did not turn ignition off. Vehicle was locked in 4th gear I think. I drove home, when I got into drive way, I put vehicle in reverse and felt a bit of a jerk, then vehicle reversed. I restarted vehicle and put it into reverse, it went into reverse smoothly with no issues. After a few hours of sitting I took it out to drive again, drove smoothly, I even put my foot down for a few seconds and zero issue.

I had my buddy scan the rover with a IID Tool, it came with the following list of codes. I have read a lot of other threads regarding the solenoid issue, some form of electrical glitches, O-ring issues.

I’m not exactly sure where to start the prognosis on the following scans, any advice would be greatly appreciated.

2004 L322 4.4 BMW ZF5HP24 - 103,000 KMs
Transmission service, diff fluid or transfer case fluids have not been changed yet. Will be placing an order on all fluids soon.

284976
284977

284978
284979
284980
284981
 

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The combination of “noise on actuator signal” and “output shaft speed sensor” faults point to an issue with the transfer box shift motor potentiometer. Can you start the car in neutral and then try shifting the transfer box into low range and then back into high again?

Phil
 

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2002-2005 Range Rover MkIII / L322
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Phil is the de facto expert on the potentiometer issue, which is perhaps the #1 most common cause for TRANS FAILSAFE PROG messages, so I'll defer to him and his many posts on the fix, but only add that RockAuto has a rebuild service for the transfer case motors through Cardone. You purchase the rebuild service, then send your transfer case motor to Cardone, and they rebuild and send it right back to you. I've done this on both my Rovers and had excellent results. Regardless of whether you use the rebuild service or not, with any functional transfer case motor on the car, you need to regularly put the car in neutral and actuate the motor to keep it from sticking or malfunctioning.

Separately, there are some other things to consider:

The #1 issue with transmission problems on these cars is due to overheating: I accept this as fact based on a lot of empirical evidence, and no compelling evidence to the contrary. Not to disrepect anyone, but in my opinion anyone who tells you that the car is designed to run at the temps it does (engine and transmission), without any long-term consequences, doesn't understand the effects of high heat on clutch packs, seals, and fluid as it breaks down at the molecular level. This is a great article on heat and the oxidizing effects on engine oil (it applies to transmission fluid too). LINK HERE.

So with that, let me just bulletize some information here, and I might do a YouTube video on this in more detail later.

  • BMW chose to run a 108 degree Celsius thermostat on the M62TU engine, for one primary purpose: to meet emissions requirements. The thermostat temp is detrimental in every way to the longevity of both the engine and transmission. In addition, plastic parts under the engine bay get heated and lose their lubricity faster than they otherwise would. HID ballasts operate hotter, everything is stressed and its operational life shortened.
  • The thermostat for the transmission opens at 80 degrees C, which is fine, but with the engine pegged to a 108 degree C thermostat, the heat from the engine ends up heating up the transmission to higher than 80 degrees c, and that's not fine.
  • There was a service recall for the aluminum liquid-to-liquid transmission cooler, as it corrodes internally on the coolant loop and inhibits the flow of coolant through it. The unit needs to be changed on any Rover nearing or exceeding 100k miles. View my YouTube video on this below for more information and only use a genuine Behr transmission cooler.
  • The transmission fluid and filter absolutely need to be changed (and when you do it, change them both once, drive the car for several months and change them again). Only do a drain and refill, never a "flush" with a shop flushing machine. And always ONLY use a genuine "Made in Germany" transmission filter, otherwise you'll have inadequate fluid flow. Because there's no drain plug on the torque converter, you can only drain so much fluid, so when you add new fluid, it combines with some of the old and the only way to get it all out is to do multiple drains and refills. If you continue to drive on old fluid, a clogged filter, AND an overheat condition, your transmission's days will be numbered. See the graph below correlating temperatures to expected failure.
  • Next, as corrosion takes hold of your coolant circuit, you can also have gunk that builds up in the radiator and inhibits proper cooling of your engine and subsequently transmission. You'll need to remove and evaluate the condition of your radiator and replace it if necessary. Don't bother trying to flush the corrosion or gunk out of a used radiator, it's impossible as the channels are very thin plates running horizontally. It can't be cleaned and must be replaced.
    • While we're talking about radiators, another valuable point is that in any automotive application, actually any application that uses a liquid-based radiator heat exchanger. Whenever you replace a radiator, you must always thoroughly flush the new radiator prior to installing it, as the manufacturing process will leave some residue that, if left in place, can clog your cooling system. This is true in any application from automotive to computer water cooling, to residential and commercial HVAC hydronic coolers. I've worked with almost all of the above applications and can attest to the importance of flushing new radiators prior to installing them.
  • Finally, if the transmission has ever been rebuilt, and the tech did not know some of the particularities about fitting the shafts back together, it's very possible that any one of a number of small o-rings could have gotten nicked and is causing issues.
Please review the image below to get a better understanding of what temperatures are good and bad for the transmission. If you ever see a message on the dash for "transmission overheat" it is far too late. I've experienced conditions where the transmission was at 140 degrees C and already well above the overheat threshold but the instrument cluster still didn't report an overheat; however the transmission ECU went into a sort of protection shift mode where it locked you into first or second gear, to help protect it. Ideally, you want your transmission to remain under 80 degrees C max if you want it to have a long life.

The crux of the problem in the 2003-2005 L322 M62TU rovers, is that the liquid-to-liquid transmission cooler couples the transmission temperature to the engine temperature. And the engine temperature is set to run far too high due to the 108 degree engine thermostat. The simplest fix is to run a modified engine thermostat (Abbes-Performance) makes a modified thermostat housing that lets you run either a 75 degree C, 80 degree C, or 87 degree C thermostat. And the second issue is to ensure that your liquid-to-liquid cooler is replaced, along with any associated coolant hoses that may have a build-up of corrosion.



Transmission Temperature Chart in Degrees Fahrenheit
by M J R, on Flickr

Conversion table:

325 F = 162 C
300 F = 148 C
275 F = 135 C
250 F = 131 C
225 F = 107 C
200 F = 93 C
175 F = 79 C

One last thing, you can use Valvoline MaxLife ATF without any issues in this transmission. I use that stuff in all of my transmissions, 4HP24, 5HP30 (Rovers), both my Mercedes SLs without any issues. It meets all the requirements of the overpriced Esso stuff, but without the stiff price. I don't skimp on anything and that ATF is perfectly fine, it's just not a fancy name brand.

 

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2002-2005 Range Rover MkIII / L322
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Discussion Starter #4
The combination of “noise on actuator signal” and “output shaft speed sensor” faults point to an issue with the transfer box shift motor potentiometer. Can you start the car in neutral and then try shifting the transfer box into low range and then back into high again?

Phil
Hey Phil I did as you said and luckily I was recording it:


As of now every time I put the vehicle into R or D it makes that loud grinding sound and I just get scared and put it either into neutral or park. While in drive the vehicle will roll back as the grinding sound is making its rounds.

This all started happening as soon as I messed with the low gear setting, I think maybe the transfer case is toast and not sure if I toasted the transmission as well.

Right now the low gear setting is not working, no light pops on the dash.

I have the TRANS FAIL SAFE PROG. code on the dash.
 

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2002-2005 Range Rover MkIII / L322
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Discussion Starter #5
Phil is the de facto expert on the potentiometer issue, which is perhaps the #1 most common cause for TRANS FAILSAFE PROG messages, so I'll defer to him and his many posts on the fix, but only add that RockAuto has a rebuild service for the transfer case motors through Cardone. You purchase the rebuild service, then send your transfer case motor to Cardone, and they rebuild and send it right back to you. I've done this on both my Rovers and had excellent results. Regardless of whether you use the rebuild service or not, with any functional transfer case motor on the car, you need to regularly put the car in neutral and actuate the motor to keep it from sticking or malfunctioning.

Separately, there are some other things to consider:

The #1 issue with transmission problems on these cars is due to overheating: I accept this as fact based on a lot of empirical evidence, and no compelling evidence to the contrary. Not to disrepect anyone, but in my opinion anyone who tells you that the car is designed to run at the temps it does (engine and transmission), without any long-term consequences, doesn't understand the effects of high heat on clutch packs, seals, and fluid as it breaks down at the molecular level. This is a great article on heat and the oxidizing effects on engine oil (it applies to transmission fluid too). LINK HERE.

So with that, let me just bulletize some information here, and I might do a YouTube video on this in more detail later.

  • BMW chose to run a 108 degree Celsius thermostat on the M62TU engine, for one primary purpose: to meet emissions requirements. The thermostat temp is detrimental in every way to the longevity of both the engine and transmission. In addition, plastic parts under the engine bay get heated and lose their lubricity faster than they otherwise would. HID ballasts operate hotter, everything is stressed and its operational life shortened.
  • The thermostat for the transmission opens at 80 degrees C, which is fine, but with the engine pegged to a 108 degree C thermostat, the heat from the engine ends up heating up the transmission to higher than 80 degrees c, and that's not fine.
  • There was a service recall for the aluminum liquid-to-liquid transmission cooler, as it corrodes internally on the coolant loop and inhibits the flow of coolant through it. The unit needs to be changed on any Rover nearing or exceeding 100k miles. View my YouTube video on this below for more information and only use a genuine Behr transmission cooler.
  • The transmission fluid and filter absolutely need to be changed (and when you do it, change them both once, drive the car for several months and change them again). Only do a drain and refill, never a "flush" with a shop flushing machine. And always ONLY use a genuine "Made in Germany" transmission filter, otherwise you'll have inadequate fluid flow. Because there's no drain plug on the torque converter, you can only drain so much fluid, so when you add new fluid, it combines with some of the old and the only way to get it all out is to do multiple drains and refills. If you continue to drive on old fluid, a clogged filter, AND an overheat condition, your transmission's days will be numbered. See the graph below correlating temperatures to expected failure.
  • Next, as corrosion takes hold of your coolant circuit, you can also have gunk that builds up in the radiator and inhibits proper cooling of your engine and subsequently transmission. You'll need to remove and evaluate the condition of your radiator and replace it if necessary. Don't bother trying to flush the corrosion or gunk out of a used radiator, it's impossible as the channels are very thin plates running horizontally. It can't be cleaned and must be replaced.
    • While we're talking about radiators, another valuable point is that in any automotive application, actually any application that uses a liquid-based radiator heat exchanger. Whenever you replace a radiator, you must always thoroughly flush the new radiator prior to installing it, as the manufacturing process will leave some residue that, if left in place, can clog your cooling system. This is true in any application from automotive to computer water cooling, to residential and commercial HVAC hydronic coolers. I've worked with almost all of the above applications and can attest to the importance of flushing new radiators prior to installing them.
  • Finally, if the transmission has ever been rebuilt, and the tech did not know some of the particularities about fitting the shafts back together, it's very possible that any one of a number of small o-rings could have gotten nicked and is causing issues.
Please review the image below to get a better understanding of what temperatures are good and bad for the transmission. If you ever see a message on the dash for "transmission overheat" it is far too late. I've experienced conditions where the transmission was at 140 degrees C and already well above the overheat threshold but the instrument cluster still didn't report an overheat; however the transmission ECU went into a sort of protection shift mode where it locked you into first or second gear, to help protect it. Ideally, you want your transmission to remain under 80 degrees C max if you want it to have a long life.

The crux of the problem in the 2003-2005 L322 M62TU rovers, is that the liquid-to-liquid transmission cooler couples the transmission temperature to the engine temperature. And the engine temperature is set to run far too high due to the 108 degree engine thermostat. The simplest fix is to run a modified engine thermostat (Abbes-Performance) makes a modified thermostat housing that lets you run either a 75 degree C, 80 degree C, or 87 degree C thermostat. And the second issue is to ensure that your liquid-to-liquid cooler is replaced, along with any associated coolant hoses that may have a build-up of corrosion.



Transmission Temperature Chart in Degrees Fahrenheit
by M J R, on Flickr

Conversion table:

325 F = 162 C
300 F = 148 C
275 F = 135 C
250 F = 131 C
225 F = 107 C
200 F = 93 C
175 F = 79 C

One last thing, you can use Valvoline MaxLife ATF without any issues in this transmission. I use that stuff in all of my transmissions, 4HP24, 5HP30 (Rovers), both my Mercedes SLs without any issues. It meets all the requirements of the overpriced Esso stuff, but without the stiff price. I don't skimp on anything and that ATF is perfectly fine, it's just not a fancy name brand.

Hey MJR,
Thank you so much for all the information. Let’s try and see if we can get this thread into a sticky considering the weight of information.
 

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LEGACY VENDOR
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I would try the fuse 37 trick to see if you can re-calibrate the shift motor. Hopefully, this will allow you to re-engage one of the transfer box ranges. Mechanical problems with the NV225 transfer box are very rare – it’s much more likely to be a shift motor/potentiometer issue.








Phil
 

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2002-2005 Range Rover MkIII / L322
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Discussion Starter #7
I would try the fuse 37 trick to see if you can re-calibrate the shift motor. Hopefully, this will allow you to re-engage one of the transfer box ranges. Mechanical problems with the NV225 transfer box are very rare – it’s much more likely to be a shift motor/potentiometer issue.








Phil
Hey Phil,
So after following the above steps, the transmission is no longer making a grinding sound when shifting into R or D. Just a very tiny bit jerky but it’s shifting smoothly.

However the low range and high range seemed to be erratic. The low range light disappears on its own and then reappears. I’m sitting in park with the handbrake on and without me even doing anything the low gear light has turned on for a few seconds, turns off, high gear shows on dash, low gear turns on again and now it’s just stuck in Lo.

 

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The way the controller knows which range the transfer box is in, is from a voltage signal from the rotary potentiometer housed inside the shift motor.







This potentiometer is problematic in older vehicles and commonly this stems from the fact that most vehicles spend their whole lives in high range and the potentiometer consequently never gets any exercise. You will see countless posts on here where people have tried, unsuccessfully, to find a source for the potentiometer to enable them to replace it without having to change the complete shift motor. Note that replacing the shift motor is a relatively straight-forward job, but new motors are eye-wateringly expensive.

I would suggest that you either try to source a second-hand shift motor (which clearly comes with the risk that you’re replacing one worn-out potentiometer with another one) or, as MJR has suggested, send your unit away for refurbishment.

There’s a post here which deals with the potentiometer in some detail : Transfer box potentiometer dimensions for gyrogypsy

Phil
 

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Registered
2002-2005 Range Rover MkIII / L322
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146 Posts
Discussion Starter #9
The way the controller knows which range the transfer box is in, is from a voltage signal from the rotary potentiometer housed inside the shift motor.







This potentiometer is problematic in older vehicles and commonly this stems from the fact that most vehicles spend their whole lives in high range and the potentiometer consequently never gets any exercise. You will see countless posts on here where people have tried, unsuccessfully, to find a source for the potentiometer to enable them to replace it without having to change the complete shift motor. Note that replacing the shift motor is a relatively straight-forward job, but new motors are eye-wateringly expensive.

I would suggest that you either try to source a second-hand shift motor (which clearly comes with the risk that you’re replacing one worn-out potentiometer with another one) or, as MJR has suggested, send your unit away for refurbishment.

There’s a post here which deals with the potentiometer in some detail : Transfer box potentiometer dimensions for gyrogypsy

Phil
Hey Phil,

Thanks for getting back. Yeah I read the potentiometer related articles too, also tried to find a potentiometer replacement but unfortunately to no avail. I found a parts Range Rover close by so might just go and buy the motor from him. New one is $1200, which is a little ridiculous considering the 2006 L322 motor can be had for around $400 new since its GM based. Yeah as MJR suggested, the rebuild through Cardone seems to be the best way to go about it. Might just buy a used motor for now, see if it fixes the issue.

After installing the new motor I suppose all I have to do is run the recalibration?
 

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Discussion Starter #10
Update:

Tried to take apart the potentiometer, miserably failed as the ceramic resistor disc popped out and cracked. Ordered a used potentiometer from eBay, $175CAD total.

Removed potentiometer from purchased motor and swapped it into my old TC motor. Everything works smoothly now; low and high gear shift as they should, no TRANS. FAIL SAFE PROG error on dash. Didn’t even have to clear with diagnostic tool.

Two things I noticed on this used motor that came in. The motor itself was not stamped with “BMW” and it didn’t say “USA” below the “BMW” like on my original motor.

The serial number written on the potentiometer removed from the used motor was the same as my original, however the number beneath it was different. On my original motor’s potentiometer the number “0352” was written in the plastic. On the potentiometer from the recently purchased motor, the number below the serial is “1220”. My vehicle is a 2004, I assume the 03-52 maybe stands for 2003-52? Not sure of the significance, I’m likely just insane and this is something I noticed.

Also those interested in a headunit upgrade, please stay tuned for a new thread on how to swap a 10.25” Android Headunit into a 2002-2004 L322.
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